Processes and apparatus for the plane (flat) rolling of band-type materials, i.e. steel and nonferrous metal strip, generally make use of high-speed cold-rolling stands provided in a rolling line in the mill and, more particularly, a multiplicity of such stands, each having working rolls defining a gap through which the strip passes at a high rate of speed. The upper and lower working roll is urged against the strip by the top backing up roll while the lower or bottom working roll is supported by the bottom backing up roll in the typical four-high mill stand.
It is known to provide in flattening lines and cold reduction lines of steel strip of this type, a plurality of nozzles to spray coolant in zones selectively and/or with quantities controlled to regulate the planarity of the rolled product.
To this end, deviations from true planarity can be measured upon the strip and the coolant discharge controlled accordingly.
In aluminum cold-rolling lines, for example, it is known to provide a cooling system in which a plurality of individual spray nozzles are trained upon the working rolls, the individual nozzles being controlled by a continuous planarity measurement by means of so-called stressometer rolls.
This process requires an apparatus in which the control valves are disposed above the strip on the mill stands or below the strip and even below the floor of the mill in a construction which permits only the nozzles to be disposed directly in the region of the gap.
Since all of the stands had to be provided with this complex control arrangement in the more common prior art techniques, the capital cost of the system was considerable and repair and maintenance was always a problem.
Furthermore, the control of the planarity left much to be desired, i.e. the rolled product still had a significant deviation from true planarity and all attempts to regulate the line to improve the planarity resulted in compromises to the extent that the product had to be considered acceptable even though the planarity deviated within a fairly wide tolerance range from the ideal.
Since steel and nonferrous metal strip requirements have increased in recent years, the problem of producing such strip with minimum deviation from true or ideal planarity has been magnified.